It's been called the “rover on steroids,” a one-ton mobile geology lab bristling with instruments that will help determine whether conditions on Mars have ever been favorable for life.
The rover — named Curiosity — is the heart of NASA's Mars Science Laboratory, a $2.5 billion mission that is the most sophisticated effort to date to look for signs of microbial life — past or present — on the so-called “red planet.”
Launched last Nov. 26, a spacecraft carrying Curiosity will land on Mars Aug. 6 if all goes according to plan. The craft will descend in a series of S-curves through the Martian atmosphere, and three minutes before touchdown a parachute will slow it down. Then, retro rockets attached to an upper stage will fire, and in the final seconds the upper stage will act as a sky crane, gently lowering Curiosity on a tether to the ground.
The Mars Science Laboratory is the latest in a long line of U.S. scientific missions to Mars dating back to 1965, when Mariner 4 flew past the planet and transmitted 21 images back to Earth.
One of NASA's greatest achievements so far has been the mission of the twin Mars rovers Opportunity and Spirit that began in January 2004. Both about the size of golf carts, the solar-powered vehicles were scheduled to roam just a few miles of the Martian surface, examining soil and rocks, for only 90 days. But they kept going, and NASA repeatedly extended their missions based on the enormous quantity of information they sent back to Earth about Mars' geology.
Spirit drove 4.8 miles before ceasing communications in 2010. Opportunity is still at work, eight years after landing, having driven more than 21 miles — it was built to drive less than one mile. Opportunity has examined four craters, including one 14 miles in diameter known as Endeavour, where it has been positioned since last fall.
Curiosity, which is about five times the size of Spirit and Opportunity, will use its instruments, including a rock-vaporizing laser, to collect and examine rock and soil, then send technical information back to Earth. Among other things, it will look for evidence of methane gas, which might suggest Mars has some form of life.
A sky crane lowers the Curiosity rover to the surface of Mars in this artist's rendering. (NASA/JPL-Caltech)
Despite its eight years on the job, Opportunity is not the longest-serving spacecraft to visit Mars. That distinction is held by Mars Odyssey, which has been in orbit around the “red planet” since 2001 and will continue for the indefinite future. In December 2010 Odyssey surpassed the previous record for Mars service held by the Mars Global Surveyor, which orbited the planet from 1997 to 2006. Among Odyssey's achievements has been the detection of hydrogen beneath the Martian surface, leading scientists to believe water might also be present.
Another major Mars program, planned by the United States in conjunction with the European Space Agency, may have fallen victim to budget cuts. Known as ExoMars, it is supposed to have two components: the Trace Gas Orbiter, to be launched in 2016, with a mission of examining the Martian atmosphere in greater detail than previous orbiters could; and two rovers, to be launched in 2018, which would dig up soil samples to be retrieved by later missions. The goal is to learn much more than is currently possible about the planet's geological history.
However, the proposed NASA budget issued Feb. 13 by the Obama administration eliminated funding for U.S. participation in ExoMars. Administration officials for months had signaled that such a cut was likely, leading the European and Russian space agencies in late 2011 to begin discussions about a joint program without U.S. participation.
The proposed withdrawal from the mission has angered Mars exploration advocates, including Robert Zubrin, founder and president of the Mars Society. Zubrin says the Obama administration “is reneging on a deal we had with the Europeans. Not only are they wrecking our own program, but they are wrecking the European program as well.”
Unless reversed by Congress, the U.S. withdrawal likely will affect a subsequent mission to retrieve the soil samples. Known as the Mars Astrobiology Explorer-Cacher (MAX-C), it was the highest-priority project in a NASA-sponsored survey of planetary science projects for the coming decade, according to the independent National Research Council. Cost estimates for the project have ranged from $2.2 billion to $4.7 billion. However, the council suggested deferring or even canceling the project if it could not be done for under $2.5 billion.
NASA said last June that it concurred with that recommendation and was examining “a significant cost reduction” to enable the project to proceed.
While most of the past and current U.S. explorations of Mars have been successful, the same cannot be said for the other great space power of the past 50 years. Since the 1960s, Russia (and its predecessor, the Soviet Union) have enjoyed partial successes in only two of 19 attempts to send spacecraft to Mars. Moscow's best result came in 1971, when its Mars 3 orbiter collected data for eight months, and a related lander got safely to the Martian surface but sent back only 20 seconds of data, according to NASA.
Russia's latest stumble came in November, when the ambitious Phobos-Grunt mission failed to get out of Earth orbit. Russian engineers tried unsuccessfully for weeks to save the spacecraft, which eventually plunged into the Pacific Ocean on Jan. 15. Russian officials initially were quoted as suggesting that a U.S. military radar installation in Alaska might have damaged Phobos-Grunt, but subsequent reports said cosmic radiation damaged the spacecraft's software.
The spacecraft included a probe that was supposed to land on the small Martian moon Phobos, scoop up soil, and then return it to Earth. If successful, the mission would have marked the first time that any object from Mars had been returned to Earth for scientific examination.
— John Felton